As is known to those skilled in the medical arts, a number of situations can arise in which it is medical necessary to provide a drain from the pleural cavity. In these cases the pleural cavity is disrupted because of, for example, a blunt trauma injury (e.g., knife wound, gunshot wound, severe automobile accidents) and intentional chest trauma, for examples such as that resulting from thoracic surgical procedures requiring the drainage of air and/or fluid from collecting in the pleural cavity. Other pleural abnormalities include pleural effusion and empyema.
In addition, after heart surgery there is the possibility of the accumulation of blood and clots, for example, in the mediastinum, specifically in the pericardial sac, which can be life threatening. Thus, a drain can be provided for mediastinal drainage to minimize the risk of cardiac tamponade.
Initially and traditionally, such chest drainage was accomplished using what has been commonly referred to as a three-bottle chest drainage system. Since then, a number of devices have been developed to mimic the three-bottle system, which devices are sometimes referred to simply as chest drainage units. Such chest drainage units include a mechanism for collecting the liquid effluent from the patient, a patient seal that acts as a one-way valve so as to allow gaseous effluent to leave the pleural cavity but prevents a gas such as air from returning to the pleural cavity and a mechanism for limiting or controlling the amount of suction that can be applied to the pleural cavity by the chest drainage unit. A line(s) also is typically provided to connect the chest drainage unit to the pleural cavity and/or the mediastinum so that fluids can be withdrawn therefrom and collected in the chest drainage unit. In addition, another portion of the chest drainage unit is connected to a negative pressure source or vacuum/suction source, so as to cause the fluid or liquid effluent to flow to the drainage device and, in the case of the pleural cavity also maintaining a negative pressure in the pleural cavity so as not to compromise the full expansion of the lung.
It is possible to develop high or excess negative pressure conditions within such chest drainage units that must be relieved so as to avoid or minimize the risk of damage to tissue surrounding the drainage tube within the patient's body. Thus, specific measures or mechanisms are put into place so that such high or excess negative pressure conditions (i.e., a more negative pressure condition) can be removed and so that normal negative operational conditions can be reestablished within the chest drainage unit.
Such high negative pressure conditions can result from a number of circumstances including, for example, patient coughing or medical personnel milking or stripping of the drainage tubing so as to cause any clots or the like to move towards the chest drainage unit. Milking is a term that is generally used to describe gentle kneading of short sections of the tubing so as to cause momentary burts of suction within the tubing. Stripping is a much more vigorous procedure during which long lengths of the tubing are compressed and released. Stripping can cause dangerously high negative pressures.
Initially, one form of protection from high or excess negative pressure condition was a manually actuated valve whereby the medical personnel would depress or push a button of the manually actuated valve so as to allow external air to be introduced into the chest drainage unit, thereby alleviating the high negative pressure condition. For this form of protection to work, however, the medical personnel must first observe the patient and determine that a high negative pressure condition exists before they would actuate the manual valve. Thus, it may take some time after the onset of the high or excess negative pressure condition before such a condition is detected by the medical personnel and rectified by manual actuation of the relief valve.
Some recent chest drainage units, particularly those units that embody a dry suction type of control mechanism, for example that shown in U.S. Pat. No. 5,989,234, have included an automatic high-pressure negative pressure relief valve alone or in combination with a manually actuated relief valve. The automatic pressure relief valve is configured so it automatically opens and closes responsive to the negative pressure conditions within the chest drainage unit. Further, such an automatic relief valve typically is configured to open when a predetermined negative pressure condition or an even more negative condition is established within the collection chamber or section of the chest drainage unit, which pressure condition is in excess (i.e., more negative) of any of the normal operating suction or negative pressure conditions that can be developed in the collection chamber or section. For example, in some chest drainage units with a dry suction control regulation device designed to maintain suction pressures up to and including −40 cm of water, the set point for the automatic negative pressure relief valve is about −50 cm of water.
One such automatic high or excessive negative pressure relief valve is the adjustable check valve found in U.S. Pat. No. 4,550,749. Material properties of the resilient valve element of this pressure relief valve, such as the rigidity of the material, dictates at what pressure and where the resilient valve element will reseal. Consequently, this valve does not close as accurately as is desired. In addition, it has been observed that the pressure differential for closure varies from valve to valve. This failure to close accurately necessarily means that more air is being admitted into the chest drainage unit than is needed to overcome the high negative pressure condition. As such, the excess air needs to be withdrawn from within the chest drainage unit in order to restore normal operational negative pressure conditions. In addition, it has been observed that this adjustable check valve has proven to be difficult to manufacture.
There is found in U.S. Pat. No. 6,024,120 another negative pressure relief valve for relieving an excess negative pressure condition, that is configured so as to function either automatically or manually. In this valve, a diaphragm is slidably moved along a length of a piston rod. One end of the piston rod is configured so as to have a plurality or more of leg like members with a void between each leg. Thus, when the diaphragm slides over the leg like members, the suction side of the valve is put into fluid communication with the atmospheric side of the valve such that air flows into the chest drainage unit.
In this valve a seal must be maintained between the diaphragm and the exterior surface of the piston rod when the diaphragm is stationary and as it moves along the length of the piston rod until the suction side of the valve is put into fluid communication with the atmospheric side of the valve. If the seal is not maintained, the relief valve will leak air into the collection chamber or collection section side of the chest drainage unit. It is possible that the medical personnel could initially misinterpret such an air leak as being representative of the presence of an air leak upstream of the chest drainage, for example in the interconnecting tubing or at the drainage site (i.e., patient). In order to establish such a seal, the diaphragm must exert a radial force urging the inner periphery of the diaphragm into sealing engagement with the exterior surface of the piston rod. Because this force necessarily retards the motion of the diaphragm, it impacts the set point of the relief valve.
It thus would be desirable to provide a new automatic excess or high negative pressure relief valve that would respond to the negative pressure differentials typically seen in chest drainage units as well as chest drainage units and methods related thereto. It would be particularly desirable to provide such a pressure relief valve and related method that would more consistently open and close at the desired negative pressure conditions in comparison to prior art pressure relief valves/devices. It also would be desirable to provide such a pressure relief valve that is easily adjusted to any one of a number of negative pressure set points or within a range of negative pressures as compared to prior art pressure relief valves/devices. Such pressure relief valves preferably would be simple in construction, and less costly than prior art valves and such methods would not require highly skilled users to utilize the valves/device.